The present invention relates to stable biocidtal compositions containing combinations of certain imidazole iodines and 3-isothiazolones. The present invention also relates to the use of low concentrations of copper salts to stabilize such compositions.
Microbicides are used commercially to prevent the growth of microbes in a variety of loci, such as cooling towers, metal working fluid systems, paints and cosmetics. One of the more important classes of microbicides is 3-isothiazolones. Many 3-isothiazolonies have achieved commercial success because they are very effective in preventing microbial growth under a wide variety of conditions and in a variety of loci. Among the most important 3-isothiazolones are 5-chloro--methyl-3-isothiazolone ("CMI"), 2-methyl-3-isothiazolone ("MI"), and mixtures thereof.
Although 3-isothiazolones are highly effective microbicides, some suffer from being unstable under certain conditions. Without the presence of a stabilizer, many 3-isothiazolones chemically degrade and lose microbicidal efficacy. Much research has been devoted to stabilizing 3-isothiazolones. A variety of stabilizers for 3-isothiazolone solutions are known and are described, for example, in U.S. Pat. No. 5,461,150 (Gironda et al) and U.S. Pat. No. 5,312,827 (Bayer et al).
Imidazolidines (which include hydantoins) are another class of Microbicides, and have been used for years in a variety of loci. The most well-known microbicide of this class is 1,3-dimethylol-5,5-dimethylhydantoin ("DMDMH"). DMDMH is generally provided as an aqueous solution, an anhyhdrous powder, or a solution in glycol. DMDMH is sold under various names, including Glydant.RTM.. These types of compounds are storage stable as supplied and do not require stabilizers to prevent chemical degradation.